A novel organic-inorganic hybrid hollow polymer capsule with rich amino/imino groups for anionic contaminant removal in wastewater: Synthesis, performance and mechanism

Herein, we developed a new organic-inorganic hybrid polymer adsorbent, termed PECP, by one-step precipitation polycondensation between polyethyene polyamine and hexachlorocyclotriphosphazene. The morphology and microstructure of PECP were investigated by FTIR, SEM, TEM, XPS, XRD and N₂ adsorption. Results show PECP owned a hollow capsule structure and lots of amino/imino groups. The adsorption capacity of PECP for anionic dye methyl orange (MO) was up to 1031.9 mg g^-1. The adsorption process was very fast. After five cycles, the adsorption capacity of PECP for MO still remained at 89 % of the initial adsorption capacity. Meanwhile, PECP delivered a high adsorption capacity for other anionic contaminants like acid chrome blue K (1003.5 mg g^-1), congo red (1152.2 mg g^-1) and diclofenac sodium (914.2 mg g^-1). In the binary systems contaminated with double dyes, the separation factors of MO for methylene blue, Rhodamine B and crystal violet were up to 450.8, 55.4 and 355.9, respectively. The experimental data unveiled that the MO removal by PECP was very consistent with the pseudo-second-order kinetic model and the Langmuir isotherm model. The removal process was spontaneous and endothermic. FTIR spectroscopy and XPS analysis confirmed the role of electrostatic force and hydrogen bond on the adsorption of MO on PECP.